1. Field of the Invention
The invention is a storable adhesive for PVC plastics, particularly post-chlorinated PVC plastics.
2 Background of the Invention
Pipes and fittings of post-chlorinated PVC are used for applications where, in addition to high internal pressures of up to 4 bars, temperatures in the range from 60.degree. to 95.degree. C. are encountered. Known adhesives for pipes and fittings of post chlorinated PVC contain between 10 and 30% by weight postchlorinated PVC having a suitable K-value and chlorine content as a binder in combination with suitable, solvents, such as tetrahydrofuran, cyclohexanone, methyl ethyl ketone, N-methylpyrrolidone, methylene chloride, acetone, ethyl acetate and the like. The adhesive can contain consistency-generating constituents such as thickeners, thixotropic agents and the like.
One of the properties, typical of post-chlorinated PVC adhesives is that, depending on the storage temperature, they give off chlorine by a process which is not fully understood and which, due to the inevitable presence of moisture in the adhesive (for example as a result of impurities in the solvent), can lead to container corrosion through the formation of hydrogen chloride. In order to store adhesives containing post-chlorinated PVC for prolonged periods without any risk of corrosion, the adhesives are preferably stored in containers of materials which withstand the chemical attack of hydrogen chloride as a result of suitable measures or by virtue of their chemical composition. Such containers include, in particular, glass vessels, polyolefin-coated metal vessels or containers of aluminum alloys. Unfortunately, containers such as these are either difficult to handle or add considerably to the cost of the adhesives.
Where standard containers based on internally tin-plated steel are used for the adhesives, gradual gelation of the adhesive is unavoidable through the introduction of iron ions, in particular at the location of soldering of the can seam in the vicinity of the flange.
The present invention is an adhesive, containing post-chlorinated PVC, which is stable in storage, even in internally tin-plated steel containers, without substantial loss of adhesive properties.